Pressure sensor configurations for implantable medical electrical leads

ABSTRACT

An implantable pressure sensor, which may be incorporated within an implantable medical electrical lead, includes an insulative sidewall, which contains a gap capacitor and an integrated circuit. The insulative sidewall of the pressure sensor includes a pressure sensitive diaphragm portion, and the gap capacitor includes a first electrode plate, which is attached to an interior surface of the diaphragm portion of the sidewall, and a second electrode plate, which is spaced apart from the first electrode plate and coupled to the integrated circuit, which is coupled, through the sidewall, to a supply contact and a ground contact. A conductive layer extends over one of the interior surface of the diaphragm portion of the sidewall and an exterior surface of the diaphragm portion; and the conductive layer is coupled to the ground contact to either shield or ground the first electrode plate.

This application is a continuation of U.S. application Ser. No.12/108,212, filed Apr. 23, 2008, now U.S. Pat. No. 7,591,185 the entirecontents of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to implantable medical electrical leadsand more particularly to pressure sensor configurations for the leads.

BACKGROUND

Implantable systems for cardiac rhythm management often employ medicalelectrical leads, which extend into the venous blood stream and couple atherapy delivery generator device to a surface of the heart. Typically,a medical electrical lead includes one or more electrodes forstimulating the heart and for sensing electrical activity of the heart.

In addition to, or in lieu of electrodes, a medical electrical lead mayinclude one more other types of sensors, for example, a pressure sensor.An exemplary pressure sensor is a microelectromechanical systems (MEMS)capacitive pressure transducer. This type of pressure sensor typicallyincludes a hermetically sealed capsule that contains a gap capacitor andan integrated circuit (IC) chip coupled thereto. Feedthroughs extendthrough a sidewall of the capsule to couple the IC chip to externalcontacts, source and ground, and the contacts are coupled to conductorsextending within the lead body. Examples of this type of sensor aredescribed United States pre-grant patent publications 2007/0107524 and2007/0199385, which are hereby incorporated by reference in theirentirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of thepresent disclosure and therefore do not limit the scope of theinvention. The drawings are not to scale (unless so stated) and areintended for use in conjunction with the explanations in the followingdetailed description. Embodiments of the present disclosure willhereinafter be described in conjunction with the appended drawings,wherein like numerals denote like elements.

FIG. 1 is a plan view, with a cut-way portion, of medical electricallead, according to one embodiment.

FIG. 2 is an exploded perspective view of a portion of the lead shown inFIG. 1.

FIG. 3A is a perspective view of a pressure sensor, according to oneembodiment.

FIGS. 3B-C are section views, through section lines A-A and B-B,respectively, of FIG. 3A, according to some embodiments.

FIG. 4A is a perspective view of a pressure sensor, according to analternate embodiment.

FIG. 4B is a plan view of an interior surface of a diaphragm portion ofa capsule of the pressure sensor shown in FIG. 4A, according to someembodiments.

FIG. 4C is a section view, through section line C-C of FIG. 4A,according to some embodiments.

FIG. 5A is a perspective view of a pressure sensor, according to yet afurther embodiment.

FIG. 5B is a section view, through section line D-D of FIG. 5A,according to some embodiments.

FIG. 5C is a section view, through section line D-D of FIG. 5A,according to some alternate embodiments.

FIG. 5D is a section view, through section line D-D of FIG. 5A,according to yet further alternate embodiments.

FIG. 6A is a perspective view of a subassembly including a pressuresensor mounted on a platform portion of a lead body, according to someembodiments.

FIG. 6B is longitudinal section view of a portion of the subassemblyshown in FIG. 6A, according to some embodiments.

FIG. 6C is a perspective view of a subassembly including the pressuresensor mounted on a platform portion of a lead body, according to somealternate embodiments.

FIG. 7 is a plan view of a medical electrical lead, according to anadditional embodiment.

FIGS. 8A-B are section views, through section line E-E of FIG. 7,according to some alternate embodiments.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description providespractical illustrations for implementing exemplary embodiments of thepresent invention. Examples of constructions, materials, dimensions, andmanufacturing processes are provided for selected elements, and allother elements employ that which is known to those of skill in the fieldof the invention. Those skilled in the art will recognize that many ofthe examples provided have suitable alternatives that can be utilized.

Electronic components, which are not shielded and/or grounded, may besusceptible to problems associated with electromagnetic interference(EMI), and implantable medical electrical leads may include suchelectronic components. The integration of shielding and/or groundinginto an implantable medical electrical lead poses some unique designchallenges. Embodiments of medical electrical leads, which are describedherein, include a pressure sensor and one or more conductive coatingsformed over a surface of at least one sidewall of the pressure sensor inorder to shield and/or ground at least a capacitive pressure transducercontained within the sidewall of the pressure sensor.

FIG. 1 is a plan view of a medical electrical lead 10, according to oneembodiment. FIG. 1 illustrates lead 10 including an insulative lead body110, which is terminated at a proximal end 18 with a pair of connectors14, 16 and is terminated at a distal end 19 by a tip electrode 162.According to the illustrated embodiment, a pressure sensor 34 is mountedto lead body 110, and another electrode 161 extends about pressuresensor 34. Electrode 161 includes an aperture 360, to expose a pressuresensitive diaphragm portion 214 of sensor 34, which is seen in theexploded perspective view of FIG. 2. FIG. 2 illustrates a platformportion 210 of lead body 110 including a mounting surface 220 on whichsensor 34 is mounted, for example, being adhered thereto, via adhesivebonding. Portion 210 may be separately formed, for example, molded froma relatively rigid plastic, and adapted for integration into lead body110. Although not shown in FIG. 2, platform 210 preferably includesconduits allowing for a plurality of conductors 100 to couple withpressure sensor 34 and electrodes 161,162. Platform 210, sensor 34 andelectrode 161 may be integrated into lead body 110, for example, asdescribed in commonly-assigned and co-pending U.S. patent applicationSer. No. 12/107,987, which is hereby incorporated by reference in itsentirety. Pressure sensor 34 is preferably constructed according tomicroelectromechanical systems (MEMS) fabrication methods and includes acapacitive pressure transducer contained by a capsule, which is formedby an insulative sidewall 342, for example, a biocompatible ceramic,such as glass, fused silica, sapphire quartz or silicon. Insulativesidewall 342 is shown including a lid portion 241 and a base portion261, wherein lid portion 241 includes pressure-sensitive diaphragmportion 214, and is attached to base portion 261, for example, via alaser fusing process, to form a sealed cavity, as is shown in FIGS.3B-C.

FIG. 3A is a perspective view of pressure sensor 34; and FIGS. 3B-C aresection views, through section lines A-A and B-B, respectively, of FIG.3A. FIGS. 3B-C illustrate a gap capacitor 310, which is contained byinsulative sidewall 342, and which includes a first electrode plate 314spaced apart from second and third electrode plates 316, 318, which arepick-off and ground, respectively. First electrode plate 314 is shownattached to an interior surface of diaphragm portion 214, so as to movewith diaphragm portion 214, in response to external changes in pressure.Plates 316, 318, which are shown attached to an interior surface of baseportion 261 of sidewall 342, remain fixed. FIG. 3C illustrates gapcapacitor 310 coupled to an integrated circuit (IC) chip 325, which iscoupled to conductive traces 301, 303. Conductive traces 301, 303 are,in turn, coupled, through insulative sidewall 342, to a ground contact31 and to a supply contact 33, respectively, by corresponding conductivevias 312 and 332. Vias 312, 332 may be hermetic feedthroughs, forexample, formed according to the teaching of aforementioned andincorporated pre-grant patent publication '524. Each of contacts 31, 33may be coupled to a corresponding conductor of plurality of conductors100 of lead 10 (FIG. 1).

Diaphragm portion 214 is indicated with cross-hatching in the sectionview of FIG. 3C, and lid portion 241 of sidewall 342 is constructedand/or supported by base portion 261 in a manner to allow discretedeformation of portion 214, in response to changes in external pressure.Although not shown in FIGS. 3B-C, a wall thickness of that area of lidportion 241 which defines diaphragm portion 214 is thinner than aremainder of lid portion 241, according to some embodiments. Methods forthe manufacture of sensor 34, from the wafer level, may be found inaforementioned and incorporated references '385 and '524.

FIGS. 3B-C further illustrate a conductive layer 350 extending over anexterior surface of sidewall 342 of pressure sensor 34, in order toprovide EMI shielding for capacitor 310, and an insulative layer 340extending over conductive layer 350. Conductive layer 350 is showncoupled to ground contact 31 by conductive via 315. Although not shown,it should be understood that insulative layer 340 may be part of a bulkof insulative material, for example, silicone rubber, that fills a gapbetween sidewall 262 of electrode 161 and sensor 34, to isolate sensor34 from an external implant environment of lead 10, and from electrode161, for example, as is described in the aforementioned application Ser.No. 12/107,987. According to the illustrated embodiment, conductivelayer 350 prevents a parasitic capacitance, which exists acrossinsulative layer 340, from significantly increasing, when pressuresensor 34 is employed within an aqueous environment of bodily fluid, andfurther reflects radiated EMI, and drains, via the coupling with groundcontact 31, conducted EMI, thereby preventing an excess charge frombuilding up on first electrode plate 314. Apart from layer 350,parasitic capacitance and/or charge build-up, may result in drift, orpressure errors, in measures of sensor 34. IC chip 325 may also beprotected from EMI, as well as from light interference effects, byconductive layer 350. According to alternate embodiments, examples ofwhich will be described below, additional EMI shielding may be includedto augment conductive layer 350 for enhanced protection of IC chip 325and capacitor 310. A source of EMI may be external equipment, separatefrom lead 10, but may more frequently be the circuit includingelectrodes 161 and 162 (FIG. 1), for example, when bipolar pacing pulsesare conducted therethrough.

Examples of suitable materials from which conductive layer 350 may beformed, include, without limitation, titanium, platinum, nickel andtantalum or titanium alloys. Methods, which are known to those skilledin the art, for example, physical vapor deposition or electroplating,may be used to form conductive layer 350. Conductive layer 350 should bethick enough to have the minimum requisite conductivity withoutcompromising the flexibility of diaphragm portion 214 for the desiredpressure responsiveness. Such a thickness of conductive layer 350 may beupwards of 200 Angstroms and varying as appropriate; according to someembodiments, the thickness is between approximately 1 micrometer andapproximately 10 micrometer.

Although FIGS. 3B-C only show a limited extent of conductive layer 350,conductive layer 350 preferably extends over almost an entirety of theexterior surface of sidewall 342 of pressure sensor 34, with just enoughclearance between conductive layer 350 and supply contact 33 to keepconductive layer 350 electrically isolated from contact 33, in order tomaximize EMI shielding for both IC chip 325 and capacitor 310. However,according to alternate embodiments, which will be described in greaterdetail, below, additional EMI shielding is provided by a separategrounded conductive sidewall, which surrounds pressure sensor 34, sothat a conductive layer, such as layer 350, need only extend over anexterior surface of the diaphragm portion of the pressure sensor.

FIG. 4A is a perspective view of a pressure sensor 44, according to analternate embodiment. FIG. 4A illustrates pressure sensor 44 including acapsule formed by an insulative sidewall 442, a conductive layer 450,which extends over an exterior surface of sidewall 442, and aninsulative layer 440, which extends over conductive layer 450. Likesensor 34, sensor 44 may be constructed according tomicroelectromechanical systems (MEMS) fabrication methods, and includesa capacitive pressure transducer contained by insulative sidewall 442.Sensor 44 may be incorporated into lead 10 (FIG. 1), in the place ofsensor 34 and, like sensor 34, insulative layer 440 of sensor 44 may bepart of a bulk of insulative material, for example, silicone rubber,that fills a gap between sidewall 262 of electrode 161 and sensor 44, toisolate sensor 44 from an external implant environment of lead 10, andfrom electrode 161.

FIG. 4A further illustrates sidewall 442 including a lid portion 441 inwhich a diaphragm portion 414 is formed, similar to diaphragm portion214 described for sidewall 342. FIG. 4B, which is a plan view of anopposing interior surface of lid portion 441, shows a first electrodeplate 416 attached to diaphragm portion 414. With reference to FIG. 4C,which is a section view through line C-C of FIG. 4A, a second electrodeplate 418 is shown attached to an interior surface of sidewall 442,spaced apart from first electrode plate 416, to form a gap capacitor410, which is coupled to IC chip 325. Conductive layer 450, which isformed as a conductive trace, electrically couples first electrode plate416 to ground contact 31, in order to drain away any charge that maybuild up on plate 416, thereby preventing drift, or pressure errors,that may otherwise result from excess charge build-up. Examples ofsuitable materials from which conductive layer 450 may be formedinclude, without limitation, gold, platinum, titanium, niobium andtantalum. A conductive via 415 couples conductive layer 450 to firstelectrode plate 416, and conductive layer 450 extends across diaphragmportion 414, to another conductive via 315, which couples conductivelayer 450 to ground contact 31.

FIGS. 4B-C illustrate lid portion 441, of sidewall 442, including aperimeter zone 464 and a more central zone 446, which zones 464, 446each correspond to an area of lid portion 441 that is fused to a baseportion 461 of sidewall 442. FIGS. 4B-C further illustrate firstelectrode plate 416 including a first portion 416A and a second portion416B, which second portion 416B is mechanically isolated from thepressure responsive movement of first portion 416A, by the fusion of lidportion 441 to base portion 461 at zone 446, so that conductive via 415,which couples electrode plate 416 to conductive layer 450, is notsubject to flex fatigue type loading.

FIG. 5A is a perspective view of a pressure sensor 54, according to yetanother embodiment; and FIG. 5B is a section view, through section lineD-D of FIG. 5A, according to some embodiments. FIGS. 5A-B illustratepressure sensor 54 including a capsule formed by an insulative sidewall542, which has an exterior surface over which a conductive layer 550extends. Pressure sensor 54 further includes an insulative layer 540,which extends over conductive layer 550. Like sensors 34, 44, sensor 54may be constructed according to microelectromechanical systems (MEMS)fabrication methods and includes a gap capacitor 510 coupled to IC chip325, which are both contained by insulative sidewall 542. Examples ofsuitable materials from which conductive layer 550 may be formedinclude, without limitation, those previously mentioned for conductivelayer 350. Conductive layer 550 should be thick enough to have theminimum requisite conductivity with out compromising the flexibility ofa diaphragm portion 514 of sidewall 542 for the desired pressureresponsiveness; such a thickness may be upwards of 200 Angstroms andvarying as appropriate.

In contrast to sensors 34, 44, ground contact 31 and source contact 33of sensor 54 are located on a lid portion 541 of sidewall, as opposed toa base portion 561. A wafer-to-wafer interconnect 512, which is formedwhen lid portion 541 is sealed to base portion 561, is included tocouple IC chip 325 to contacts 31, 33, for example, at correspondingvias (—only a via 552 for ground contact 31 may be seen in the sectionview of FIG. 5B). Interconnect 512 may be formed by depositingconductive materials on opposing sides of base portion 561 and lidportion 541, and then, when the opposing sides are brought together inorder to seal lid portion 541 to base portion 561, the conductivematerials are melted together, by local or global heating, for example,during the sealing process. Sensor 54 may be incorporated into lead 10(FIG. 1), in the place of sensor 34 and, like sensor 34, insulativelayer 540 of sensor 54 may be part of a bulk of insulative material, forexample, silicone rubber, that fills a gap between sidewall 262 ofelectrode 161 and sensor 54, to isolate sensor 54 from an externalimplant environment of lead 10, and from electrode 161.

FIGS. 5A-B further illustrate diaphragm portion 514 recessed from anexterior surface of lid portion 541 of sidewall 542. A gap capacitor 510is formed by a first electrode plate 515, which is attached to aninterior surface of diaphragm portion 514, and a second electrode plate516, which is spaced apart from first plate 515 and attached to aninterior surface of base portion 561. According to the illustratedembodiment, sensor 54 includes another conductive layer 555, whichextends over an interior surface of lid portion 541 to couple firstelectrode plate 515 to ground contact 31. Conductive layer 555 ispreferably formed as conductive trace, similar to that previouslydescribed for conductive layer 450, and is coupled, through sidewall542, by conductive via 552, to ground contact 31. Thus sensor 54includes both grounding of electrode plate 515, by conductive layer 555,to drain away charge that may build up thereon, and an EMI shield, whichis formed by conductive layer 550 extending over an exterior surface ofsidewall 542. According to some embodiments, in order to further protectcapacitor 510 and IC chip from EMI, layer 550 extends over almost anentirety of the exterior surface of sidewall 542, excluding a gap forelectrical isolation of conductive layer 550 from contact 33. Accordingto some alternate embodiments, for example, like those illustrated inFIGS. 5C-8B, the extent of layer 550 is more limited so that EMIshielding may need to be augmented by an additional shielding member.

FIG. 5C is a section view through section line D-D of FIG. 5A, accordingto some alternate embodiments, wherein an internal conductive layer 565extends between sidewall 542 and IC chip 325 to act as a shield member,which provides additional EMI shielding for chip 325. Layer 565 may beformed, for example, from a solder material. Examples of suitable soldermaterials include, without limitation, both lead-based and lead-freesolder alloys, which may be flux cored or fluxless pre-forms of thefollowing alloys and combinations thereof: tin-based, gold-based, andindium-based. A thickness of a solder pre-form for layer 565 may beapproximately 25 micrometers or approximately 50 micrometers. FIG. 5D isa section view through section line D-D of FIG. 5A, according to yetfurther alternate embodiments, wherein a capacitor array 575, which iscoupled to IC chip 325 in a flip chip configuration, extends betweensidewall 542 and IC chip 325 to act as a shield member, which providesadditional EMI shielding for chip 325.

FIG. 6A is a perspective view of a subassembly including pressure sensor54 mounted on a platform portion 610 of a lead body, for example, leadbody 110 (FIG. 1). Like platform portion 210, which is illustrated inFIG. 2, portion 610 includes a mounting surface 620 on which sensor 54is mounted, for example, being adhered thereto, via adhesive bonding.Portion 610 may be separately formed, for example, molded from arelatively rigid plastic, and adapted for integration into lead body110. According to the illustrated embodiment, sensor 54 and platformportion 610, may be inserted into electrode 161, such that conductivesidewall 262 of electrode 161 surrounds sensor 54, in the same way thatsidewall 262 surrounds sensor 34, as illustrated in FIG. 1. FIG. 6Aillustrates ground and source contacts 31, 33 coupled by laser ribbonbonds LRB to respective conductive inserts 621, 622. Conductive inserts621, 622 may have been incorporated into an insulative bulk of platformportion 610 via insert molding.

Although not shown, one of the plurality of conductors 100 (FIG. 1),which extends within lead body 110, from one of connectors 14, 16, iscoupled to conductive insert 621, for grounding, and another of theplurality of conductors 100, extending from the same connector, iscoupled to insert 622 as a source. FIG. 6A further illustrates platformportion 610 including a by-pass lumen 650, which forms a passageway,alongside pressure sensor 54, in which another of the plurality ofconductors 100 extends to couple tip electrode 162 to a contact of theother of connectors 14, 16.

FIG. 6B is a longitudinal section view of the subassembly shown in FIG.6A, according to some embodiments. FIG. 6B illustrates a conductivelayer 62 forming mounting surface 620 for pressure sensor 54. Accordingto the illustrated embodiment, conductive layer 62 is grounded by acoupling with conductive insert 621, for example, via another laserribbon bond, thereby providing additional EMI shielding for IC chip 325and capacitor 510 of pressure sensor 54. FIG. 6B further illustratesby-pass lumen 650 including a conductive liner 65 overlaid with aninsulative layer 605 to isolate liner 65 from the conductor of theplurality of conductors 100 that extends within lumen 650 when thesubassembly is integrated into lead body 110 (FIG. 1). It should benoted that insulating layer 605 may not be necessary if the conductor,which extends through lumen 650, includes an outer insulative layer, orjacket. As an alternative to, or in addition to conductive layer 62,conductive liner 65 acts to provide additional EMI shielding for IC chip325 and capacitor 510 of pressure sensor 54, being grounded by acoupling with conductive insert 621, for example, by conductive viaextending within the insulative bulk of platform portion 610, asillustrated.

FIG. 6C is a perspective view of a subassembly including pressure sensor54 mounted on a platform portion 610′ of a lead body, for example, leadbody 110 (FIG. 1), according to some alternate embodiments. FIG. 6Cillustrates a conductive shroud 625 extending about pressure sensor 54and including a base sidewall 625A and a pair of upper sidewalls 625B.Base sidewall 625A extends between sensor 54 and a mounting surface620′, of platform portion 610′, and is grounded, via another laserribbon bond LRB′ coupling with conductive insert 621. Pair of uppersidewalls 625B extend over pressure sensor 54 and are spaced apart fromone another to form an opening in order to expose diaphragm portion 514of pressure sensor 54. According to the illustrated embodiment, and withreference back to FIGS. 5B and 6B, conductive shroud 625, along withconductive layer 550, which extends over diaphragm portion 514, provideEMI shielding for sensor 54. With further reference to FIG. 6C, shroud625 includes another opening, located at that end which is in proximityto conductive inserts 621, 622. Pressure sensor 54 has been insertedinto the other opening extends therefrom for the LRB couplings. Althoughnot shown, when the subassembly of FIG. 6C is incorporated into a lead,such as lead 10 of FIG. 1, a bulk of insulative material, for example,silicone rubber, fills a gap between sidewall 262 of electrode 161 andconductive shroud 625, in order to isolate shroud 625 from electrode161, and further extends between shroud 625 and portions of pressuresensor 54, in order to isolate source contact 33, conductive insert 622and the associated LRB from the grounded components of the subassembly.

FIG. 7 is a plan view of a medical electrical lead 70, according toanother embodiment. FIG. 7 illustrates lead 70, like lead 10 of FIG. 1,including connectors 14, 16, lead body 110, and tip electrode 162. Lead70 differs from lead 10 in that a pressure sensor 34′ is included in alead body subassembly 710 that includes a grounded conductive housing861 rather than an electrode. Alternate embodiments of pressure sensor34′ are shown, via section views through section line E-E in FIGS. 8A-B.According to each of the embodiments illustrated in FIGS. 8A-B, housing861, which is formed by a grounded conductive sidewall 855, for example,titanium, contains pressure sensor 34′ in a cavity 810 thereof. Sidewall855 includes an aperture 860 extending therethrough to expose diaphragmportion 214 of insulative sidewall 342 of pressure sensor 34′. Cavity810 of housing 861, besides containing sensor 34′, may contain aninsulative filler material, for example, to support sensor 34′ thereinand/or to isolate contacts 31, 33 and their respective couplings fromone another. It should be noted that sensor 34′ includes gap capacitor310 and IC chip 325, similar to sensor 34, illustrated in FIGS. 3A-C.

FIGS. 8A-B illustrate source contact 33 of sensor 34′ coupled to afeedthrough pin 803, and ground contact 31 of sensor 34′ coupled toconductive sidewall 855. According to the illustrated embodiment,feedthrough pin 803 is located for coupling to that conductor ofconductors 100 (FIG. 1), which serves as the pressure sensor sourceconductor for lead 70, and is isolated from conductive sidewall 855 byan insulator 813, in a feedthrough configuration known to those skilledin the art. Grounded conductive sidewall 855 provides EMI shielding forIC chip 325 of sensor 34′ (not shown in FIGS. 8A-B—see FIG. 3C).Sidewall 855 may be grounded via a coupling to that conductor ofconductors 100, which serves as the grounded conductor for lead 70.FIGS. 8A-B further illustrate housing 861 including at least one by-passlumen 80, through which one or more of conductors 100 may extend tocouple with respective electrodes 162 and 761 (FIG. 7), which arelocated distal to pressure sensor 34′. Lumen 80 is shown including aninsulative liner 801, which may not be necessary if the conductor(s),which extend therethrough includes an insulative outer layer, or jacket.According to alternate embodiments, lead 70 need not include one or bothof electrodes 162, 761, and, if neither of electrodes 162, 761 isincluded on lead 70, by-pass lumen 80, of housing 861, and one ofconnector legs 16, 14 are not necessary.

According to the illustrated embodiments, in order to further shieldpressure sensor 34′ from EMI, a grounded conductive layer 850 (FIG. 8A),or 85 (FIG. 8B) spans aperture 860, which extends over diaphragm portion214 of insulative sidewall 342 of sensor 34′. FIGS. 8A-B show layers850, 85 grounded via contact with a perimeter of aperture 860 ofgrounded conductive sidewall 855.

FIG. 8A illustrates grounded conductive layer 850 extending over aninsulative layer 840, which insulative layer 840 overlays diaphragmportion 214 of pressure sensor 34′, and which may be an extension of theaforementioned filler material that surrounds sensor 34′ within cavity810. Examples of suitable materials from which conductive layer 850 maybe formed include, without limitation, those previously mentioned forconductive layer 350. Alternatively, layer 850 may be formed from aconductive polymer material, for example, a silicone rubber filled withconductive particles, such as the electrically conductive R-2637silicone sold by NuSil Technology. Conductive layer 850 should be thickenough to have the minimum requisite conductivity without compromisingthe flexibility of diaphragm portion 214 for the desired pressureresponsiveness. Such a thickness of conductive layer 850 may be upwardsof 200 Angstroms and varying as appropriate. FIG. 8A further illustratesan outer insulative sheath 845 surrounding housing 861, which sheath 845may be an extension of an outer insulation of lead body 110, forexample, being formed from either a silicone rubber or a polyurethanematerial that is commonly employed for lead body outer insulations.

FIG. 8B illustrates grounded conductive layer 85 contained withinaperture 860, between insulative layer 840 and an outer insulativesheath 845′, which surrounds housing 861. Like sheath 845, insulativesheath 845′ may be an extension of the outer insulation of lead body110. According to some embodiments, conductive layer 85 comprises aconductive fluid, for example, saline.

In the foregoing detailed description, the invention has been describedwith reference to specific embodiments. However, it may be appreciatedthat various modifications and changes can be made without departingfrom the scope of the invention as set forth in the appended claims.

1. A pressure sensor comprising: an insulative sidewall including apressure sensitive diaphragm portion; a gap capacitor contained by theinsulative sidewall, the gap capacitor including a first electrode plateand a second electrode plate, the first electrode plate being attachedto an interior surface of the diaphragm portion of the insulativesidewall and the second electrode plate being spaced apart from thefirst electrode plate; an integrated circuit contained by the insulativesidewall, the integrated circuit being coupled to the second electrodeplate; a supply contact and a ground contact, each contact beingindependently coupled, through the insulative sidewall, to theintegrated circuit; and a conductive layer extending over an exteriorsurface of the diaphragm portion of the insulative sidewall, theconductive layer being coupled to the ground contact; and a conductivesidewall extending about the pressure sensor, the conductive sidewallincluding an aperture extending therethrough and being approximatelyaligned with the pressure sensitive diaphragm portion of the insulativesidewall of the pressure sensor.
 2. The sensor of claim 1, wherein theconductive sidewall is isolated from the conductive layer of thepressure sensor, and forms an electrode.
 3. The sensor of claim 1,wherein the conductive sidewall is grounded.
 4. The sensor of claim 3,wherein the conductive sidewall is coupled to the ground contact of thepressure sensor and the conductive layer of the pressure sensor iscoupled to the ground contact via contact with the conductive sidewall.5. The sensor of claim 4, further comprising an insulative layerextending between the conductive layer and the exterior surface of thediaphragm portion of the insulative sidewall.
 6. The sensor of claim 5,further comprising an outer insulative layer extending over the apertureof the conductive sidewall, and wherein the conductive layer of thepressure sensor comprises a conductive fluid contained between theinsulative layer of the pressure sensor and the outer insulative layer.7. The sensor of claim 1, further comprising an insulative layerextending over the conductive layer of the pressure sensor.
 8. Thesensor of claim 1, wherein the conductive layer of the pressure sensorextends over an entirety of the exterior surface of the diaphragmportion of the insulative sidewall.
 9. The sensor of claim 1, whereinthe conductive layer of the pressure sensor extends over an entirety ofthe exterior surface of the diaphragm portion of the insulativesidewall, and over an exterior surface of a majority of a remainder ofthe insulative sidewall.
 10. The sensor of claim 1, wherein the pressuresensor further comprises another conductive layer extending over aninterior surface of another portion of the insulative sidewall, theother portion being adjacent to the diaphragm portion of the insulativesidewall, and wherein the other conductive layer couples the firstelectrode plate to the ground contact.
 11. The sensor of claim 1,wherein the conductive layer of the pressure sensor is further coupled,by a conductive via, through the insulative sidewall, to a portion ofthe first electrode plate.
 12. The sensor of claim 11, wherein theportion of the first electrode plate is mechanically isolated from thediaphragm portion of the insulative sidewall.
 13. The sensor of claim 1,wherein the integrated circuit is mounted to a portion of the insulativesidewall and the pressure sensor further comprises a shield memberextending between the integrated circuit and the portion of theinsulative sidewall to which the integrated circuit is mounted.